Valley fever is hard to diagnose, even harder to treat, and potentially fatal—and the number of cases is rising dramatically.

Karen Deeming was a healthy 48-year-old living in Los Banos, California, and working on her master's degree in anthropology and archaeology. Then, in late 2012, a few weeks after returning from a dig in Mariposa, California, Karen began to feel sick. A chest x-ray turned up bilteral pneumonia and masses in her lungs.

What followed was eight months of debilitating illness. And she's not better yet.

If you suspect that Karen had lung cancer, you're wrong. She had something else—and she isn't alone. Cases of her illness are on the rise: In 1998, there were 2,000. In 2011, there were around 23,000.

To find out what Karen's illness is—and whether you're at risk—watch the video above.